Networking Protocols

1
Chapter 6

• Networking Protocols

2
Introduction

• Topics
• Protocol Basics
• Protocol Characteristics
• Transmission Control Protocol/Internet Protocol
• Network Access Layer Protocols
• Internet Layer Protocols
• Transport Layer Protocols
• Application Layer Protocols

3
Protocol Basics

• A protocol is a set of rules that determines how
  computers exchange information over a network
  medium
• A wide variety of communication protocols exist,
  and many of them rely on others for operation
• Groups of related protocols are often called
  stacks or protocol stacks

4
Protocol Characteristics

• Data packets can be sent over a medium using any
  one of a number of protocols
• Protocols can be either standard or proprietary
• Standard protocols
• Support universal communication so equipment from
  different manufacturers can interact

5
Proprietary Protocols

• Proprietary protocols are vendor specific and are
  usually protected by patents or other legal
  stipulations
• Proprietary protocols include
• XNS
• NetBIOS
• IPX/SPX
• AppleTalk
• DECNet

6
Xerox Network System (XNS)

• XNS is a suite of protocols created by Xerox in
  the late 1970s for Ethernet networks
• XNS is rarely used in new networks today

7
NetBios

• The Network Basic Input/Output System (NetBIOS)
  interface was developed in 1983 for IBM
• The intention was to allow applications on
  different computers to communicate within a local
  area network
• NetBIOS was not designed for large networks

8
IPX/SPX

• Novell introduced Internetwork Packet
  Exchange/Sequenced Packet Exchange (IPX/SPX) in
  the early 80s
• This stack was based on the XNS network protocol
  family
• IPX is the Network layer protocol
• SPX is the Transport layer protocol

9
AppleTalk

• AppleTalk is Macintoshs networking protocol
• It is designed to be a flexible, simple, and
  inexpensive network means for connecting
  computers, peripherals, and servers
• Newer versions of Macintosh operating systems use
  TCP/IP and SMB as default protocols rather than
  AppleTalk
• AppleTalk is a protocol and LocalTalk is a media
  type

10
DECnet

• DECnet is a proprietary network protocol designed
  by Digital Equipment Corporation
• Currently two versions of DECnet are in use
• DECnet Phase IV which is based on the Phase IV
  Digital Network Architecture (DNA)
• DECnet/OSI also called DECnet Phase V is a
  layered model

11
Transmission Control Protocol/Internet Protocol

• TCP/IP is considered the language of the Internet
• It is the most widely used protocol today
• It is a suite, or stack, of small, specialized
  protocols
• Because of its routing ability, TCP/IP has become
  the standard for many LANs, as well as for the
  Internet

12
Transmission Control Protocol/Internet Protocol

• In the early 1970s, the Department of Defense
  funded ARPA to design a new set of computer
  communication protocols that would allow multiple
  networks to be interconnected in a flexible and
  dynamic way
• The protocol developed was originally called
  Network Control Protocol
• This success led to the implementation of the two
  main Internet protocols
• These are Transmission Control Protocol and
  Internet Protocol (TCP/IP)

13
Transmission Control Protocol/Internet Protocol

• The TCP/IP suite maps the seven layers of the OSI
  model to a four-layer model
• The TCP/IP model focuses more on
  interconnectivity than on functional layers

14
Internet and OSI Model
15
Transmission Control Protocol/Internet Protocol

• The TCP/IP model is also called the Internet
  reference model
• Layers
• Network Access
• Internet
• Transport
• Application

16
The TCP/IP Protocol Suite
17
Network Access Layer Protocols

• The Network Access layer is the lowest layer in
  the model
• It Maps to Layers 1 (Physical) and 2 (Data Link)
  of the OSI model
• It is responsible for the framing (DL) and
  physical delivery of datagrams

18
Network Access Layer Protocols

• Access Layer Protocols deliver data to computers
  and devices on the network
• These include Serial Line Interface Protocol
  (SLIP) and Point-to-Point Protocol (PPP)
• These protocols support serial data transmission
  over a modem

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Network Access Layer Protocols

• Other Network Access protocols
• the Address Resolution Protocol (ARP)
• the Reverse Address Resolution Protocol (RARP)
• Provide a means of mapping IP addresses to MAC
  addresses
• These protocols provide a means for last hop
  message delivery

20
Local ARP Broadcast
21
RARP Broadcast Example
22
Internet Layer Protocols

• The layer above the Network Access layer is
  called the Internet layer
• It manages the routing of packets that are to be
  forwarded on to different networks
• It relies on routable protocols for delivery

23
Internet Layer Protocols

• The Internet Protocol (IP) is responsible
  addressing and routing of data packets
• Routing tables created by routing protocols are
  used to forward messages from one network to
  another
• It is a low overhead, best effort delivery
  protocol

24
The Internet Layer Protocols

• IP
• ICMP
• ARP
• RARP

25
IP Message Format

• IP Packets or datagrams consist of a header, data
  (payload), and a trailer
• The header contains routing information
• Trailers contain a checksum value, which is used
  to determine if data was corrupted during
  transmission

26
IP Header
27
Packet Delivery

• IP compares the destination address in the packet
  header to router table addresses
• If the address corresponds to a local network,
  the datagram is delivered to the appropriate
  computer
• If the address corresponds to a remote network,
  the packet is passed to a router for delivery

28
Routing Controls

• Time to Live (TTL)
• prevents packets from circulating on the network
  forever
• The TTL value is decremented by one each time the
  packet traverses a router (each hop)
• Default value is usually 120
• Fragmentation Routers may break oversize
  packets into fragments, then route the individual
  fragments, which are reassembled at the
  destination computer

29
Fragmentation

• Each subnetwork has a maximum transmission unit
  (MTU), which is the largest packet it can
  transfer
• A datagram received from one network may be too
  large to be transmitted as a single packet on
  another network
• Fragmentation is the process of dividing a packet
  into smaller pieces

30
Internet Control Message Protocol

• ICMP
• Internet layer protocol
• uses IP to send its messages
• uses IP as if it was higher-level protocol
• used as an aid for other protocols
• used to test for connectivity and search for
  configuration errors in a network

31
ICMP Error Messages

• Destination Unreachable message returned to
  sender if a router cannot forward an IP datagram
• Buffer Full message returned until congestion
  due to full buffer has abated
• Hops an IP datagram has passed through its
  allotted number of routers
• Ping ICMP echo messages are returned to sender
  if destination exists and is reachable
• Traceroute ICMP timeouts used to discover path
  a packet takes as it traverses an internetwork

32
PING

• Used to test connectivity
• uses the ICMP echo function
• A small packet containing an ICMP echo message is
  sent through the network to a particular IP
  address
• The computer that sent the packet then waits for
  a return packet
• If the connections are good and the target
  computer is up, an echo message is returned to
  the sender

33
Traceroute

• Originally developed for the Unix operating
  system
• used to track the path a packet takes from sender
  to destination
• Calculates travel time for each hop
• uses an ICMP echo request packet to determine the
  path

34
Transport Layer Protocols

• The protocol layer above the Internet layer
• provides a reliable communication service so that
  extended two-way conversations may take place
• responsible for providing end-to-end data
  integrity

35
Key Features of TCP and UDP
36
Transport Layer Protocols

• Transmits data as a stream of characters
• initiates and terminates the connections between
  sender and receiver
• Two main protocols
• Transmission Control Protocol (TCP)
• User Datagram Protocol (UDP)

37
Protocols That Use TCP and UDP
38
Transmission Control Protocol (TCP)

• provides connection-oriented data transmission
• supports multiple data streams
• provides for flow and error control
• uses sequence numbers and acknowledgements to
  guarantee delivery

39
TCP Connections

• TCP communications are port to port
• A socket is an IP address plus a port number
• Well-defined port numbers have been assigned to
  common applications

40
Port Numbers

• Used to communicate with upper layers by keeping
  track of conversations with different services
  (applications)
• Well-Known port numbers define different
  application locations on the server that hosts
  the applications

41
Well-Known Port Numbers
42
TCP Segment Format
43
User Datagram Protocol (UDP)

• a connectionless protocol
• Low overhead - does not provide either sequencing
  or acknowledgements
• used a lot in telephony traffic and the Remote
  Procedure Call (RPC)
• UDP does not provide the reliability that TCP
  provides

44
UDP Segment Format
45
Application Layer Protocols

• The top layer in the Internet reference model
• Provides applications access to network services

46
Application Layer Protocols

• Telnet remote client access to resources on a
  Telnet server
• FTP reliable file transport using TCP requires
  authentication
• TFTP Unreliable file transport using UDP
• NFS allows file sharing on different platforms
• SMTP delivers mail to a server use POP or IMAP
  to retrieve mail
• LPD for printer sharing
• X Window graphical interface for client/server
  applications
• SNMP Provides network management by polling
  capable devices
• DNS maps host names to IP addresses
• DHCP provides IP address configuration to
  workstations

47
File Transfer and Remote Access

• File Transfer Protocol (FTP) which allows files
  to be uploaded and downloaded on port 21
• Telnet which uses terminal emulation for access
  to remote hosts using port 23
• Both FTP and Telnet use TCP as their Transport
  layer protocol

48
Mail and Internet

• Simple Mail Transfer Protocol (SMTP) which
  supports basic message delivery services to mail
  servers on port 25
• HyperText Transfer Protocol (HTTP) which is a
  low-overhead Web browser service protocol that
  uses port 80

49
Management and News

• Simple Network Management Protocol (SNMP) which
  uses UDP port 161 to collect information from
  network devices.
• Network News Transfer Protocol (NNTP) handles
  distribution and posting of news articles using
  port 119

50
Address Assignment and Name Mapping

• Dynamic Host Configuration Protocol (DHCP) allows
  for automatic IP addressing
• Domain Name Service (DNS) uses UDP port 53 for
  resolving domain names to IP addresses